Photomasks may be used in photolithographic systems to define patterns on semiconductor wafers in order to manufacture integrated circuits. Processing situations, however, may distort the resulting pattern defined on the wafer. For example, optical diffraction may cause the pattern defined on a wafer to differ from the pattern of the mask.
A mask pattern may be modified to compensate for these deviations. According to a known technique, an etch model may be used to modify a mask pattern. For a specific mask pattern, an etch model may be used to estimate the resulting pattern defined on the wafer after the etching process. The mask pattern may be modified in accordance with the estimate. According to another known technique, a rule-based table may be used to correct a mask pattern. A rule-based table includes rules that a mask pattern may be required to satisfy. The mask pattern may be modified to satisfy the rules. These known techniques, however, may yield unsatisfactory results in certain situations. It is generally desirable to have satisfactory results.